Notes from the Naturalist
Cycles: The Cosmic Mystery
It's spring, No Wait! It is now summer in the Gulf of Maine
As we move through the early spring past the Equinox, the dawns are earlier, the days are longer and the nights later. The sun's more direct light warms the ground and sap rises in trees. Rivers froze in winter, release huge bursts of icy water packed with nutrient into the Gulf of Maine causing enormous phytoplankton blooms in the cold waters of the Gulf. The sun provides these organisms the energy needed to rapidly multiply and as they do voracious zooplankton come to Nature's table to dine upon them. Fish of all sizes and seabirds soon join in the feeding frenzy. At last, the most conspicuous of the spring arrivals come to the party. They are the great whales of the Gulf of Maine.
Based on their feeding strategies, whales are classified into two groups. One is the Odontocetes, or toothed whales, which include dolphins, porpoises, and the rarer orcas of the Gulf. The other group is the Mysticetes, the baleen whales that are the majority of our endangered great whales. The word mysticetes derives from the Greek word mystax or mustache, referring to the plates of baleen hanging from their upper jaw. The ends are covered by hairy bristles that strain and capture the plankton and small fish that make up these whales diet. Additionally, our great whales, except the Right Whale, are called rorquals, a term from Norwegian that refers to the folds that line the whales' throats. As these whales take in copious amounts of water, these pleats allow its throat to expand and fill with seawater and food. It squirts the water through the baleen plates and captures its prey with a flick of its great tongue (See Resources 1.).
Closer to shore, clammers become active in early May digging down 8-14 inches into the exposed mudflats at low tide for soft shelled clams (Mya arenaria). Clams use their rubbery necks to siphon in seawater, which they filter for their share of the plankton bounty. Smaller in structure, mussels are another shellfish that filters plankton from the water. The most common is the blue mussel (Mytilus edilus), which lives in the rocky intertidal zone. A planktonic bloom called red tide can contaminate both and make them unfit for humans to eat. Check with your local shellfish warden before consuming these popular delicacies.
Anadromous herring, both alewives, and blueback, begin running in May and end in early June. Anadromous fish are born in fresh water, migrate to the sea and live there as adults, and complete their life cycle by returning to their birth stream to spawn. Some of these fish can perform this cycle more than once while others only get one chance.
The full moon of June is called the Strawberry moon (See Resources 3.) and, as strawberries ripen in the fields, another ancient but predictable arrival occurs, the Horseshoe Crab (Limulus polyphenus). Having lived in deeper waters offshore where they gorged on smaller invertebrates, they emerge on Gulf beaches by the June full moon (see Resources 3.). This “crab,” is not a crab at all, but is instead more closely related to spiders and scorpions. Despite their fearsome appearance, they neither bite nor sting. Empty shells litter beaches, but these are usually “molts” out of which the animals have wriggled. Horseshoe crabs are descendants of early trilobites that lived on the ocean floor as many as 400 million years ago. They also help to save lives as a protein in their blood is used to test for bacterial toxins during medical operations. Their strings of greenish eggs are a bounty for migrating shorebirds like the red knot.
June 21, the Summer Solstice, is the day the North Pole is closest to the Sun. It is the longest day of the year. As we approach the Solstice, perhaps we should take a minute to consider why do we have seasons? A year we define as one revolution of the sun, but what causes seasons? Many think that summer heat is a result of the earth being closer to the sun and winter cold a result of it being further away. This is not so, what creates the seasons is the “tilt” of the earth. As it spins in summer, the Earth is tilted 23.5 degrees closer to the sun. The northern hemisphere where we live gets maximum exposure to sunlight even while being further away in its orbit. Six months from now, at the other end of its orbit, the northern hemisphere will be tilted away from the sun at the winter solstice, and the amount of light and heat will minimize even though our planet is in a closer orbit to the sun. That is easy to understand right! Enjoy the summer as you ponder that cosmic mystery!
1. Thurston, Harry 2011 The Atlantic Coast: A Natural History, Greystone Books, Vancouver BC pp164-5
2. Schmitt, Catherine 2008 A Coastal Companion: A Year in the Gulf of Maine Tillbury House Gardiner, Me pp119
3. Ibid pp 119-120
John Halloran is the Director of Science for GOMI and a member of the GOMI Guide Team. John’s interests focus on the ocean environment where he pursues educational adventure travel, research, and recreation by sail, paddle, and scuba.John is the founder and director of Adventure Learning, Newburyport, MA, which has been involved with educational outreach in area schools and recreational programs for teens and adults since 1980. A long-time educator, John was at the forefront of the experiential education movement in the U.S.For 36 years, he taught natural science in the Newburyport Public Schools. John has special interest and expertise in teacher training and standards for learning in math and science. His role has included direct teaching, teacher training, program development, grant writing, and developing partnerships with professionals in the field.